Buggy code:
public class Combo extends Composite { boolean noSelection ; boolean ignoreModify ; boolean ignoreCharacter ; int visibleCount = 5 ; public static final int LIMIT ; static final int CBID_LIST = 1000 ; static final int CBID_EDIT = 1001 ; static int EditProc ; static int ListProc ; static final int ComboProc ; static final TCHAR ComboClass = new TCHAR ( 0 , "COMBOBOX" , true ) ; public Combo ( Composite parent , int style ) { } public void add ( String string ) { } public void add ( String string , int index ) { } public void addModifyListener ( ModifyListener listener ) { } public void addSelectionListener ( SelectionListener listener ) { } public void addVerifyListener ( VerifyListener listener ) { } int callWindowProc ( int hwnd , int msg , int wParam , int lParam ) { } boolean checkHandle ( int hwnd ) { } protected void checkSubclass ( ) { } static int checkStyle ( int style ) { } public void clearSelection ( ) { } public Point computeSize ( int wHint , int hHint , boolean changed ) { } public void copy ( ) { } void createHandle ( ) { super . createHandle ( ) ; <START_BUG> state &= ~ ( CANVAS ) ; <END_BUG> int hwndText = OS . GetDlgItem ( handle , Combo . CBID_EDIT ) ; if ( ( hwndText != 0 ) && ( ( Combo . EditProc ) == 0 ) ) { Combo . EditProc = OS . GetWindowLong ( hwndText , GWL_WNDPROC ) ; } int hwndList = OS . GetDlgItem ( handle , Combo . CBID_LIST ) ; if ( ( hwndList != 0 ) && ( ( Combo . ListProc ) == 0 ) ) { Combo . ListProc = OS . GetWindowLong ( hwndList , GWL_WNDPROC ) ; } if ( ( ( style ) & ( SWT . SIMPLE ) ) != 0 ) { int flags = ( ( OS . SWP_NOZORDER ) | ( OS . SWP_DRAWFRAME ) ) | ( OS . SWP_NOACTIVATE ) ; SetWindowPos ( handle , 0 , 0 , 0 , 16383 , 16383 , flags ) ; SetWindowPos ( handle , 0 , 0 , 0 , 0 , 0 , flags ) ; } } public void cut ( ) { } int defaultBackground ( ) { } void deregister ( ) { } public void deselect ( int index ) { } public void deselectAll ( ) { } public String getItem ( int index ) { } public int getItemCount ( ) { } public int getItemHeight ( ) { } public String [ ] getItems ( ) { } String getNameText ( ) { } public int getOrientation ( ) { } public Point getSelection ( ) { } public int getSelectionIndex ( ) { } public String getText ( ) { } public int getTextHeight ( ) { } public int getTextLimit ( ) { } public int getVisibleItemCount ( ) { } boolean hasFocus ( ) { } public int indexOf ( String string ) { } public int indexOf ( String string , int start ) { } int mbcsToWcsPos ( int mbcsPos ) { } public void paste ( ) { } void register ( ) { } public void remove ( int index ) { } public void remove ( int start , int end ) { } public void remove ( String string ) { } public void removeAll ( ) { } public void removeModifyListener ( ModifyListener listener ) { } public void removeSelectionListener ( SelectionListener listener ) { } public void removeVerifyListener ( VerifyListener listener ) { } boolean sendKeyEvent ( int type , int msg , int wParam , int lParam , Event event ) { } public void select ( int index ) { } void setBackgroundPixel ( int pixel ) { } void setBounds ( int x , int y , int width , int height , int flags ) { } void setForegroundPixel ( int pixel ) { } public void setItem ( int index , String string ) { } public void setItems ( String [ ] items ) { } public void setOrientation ( int orientation ) { } public void setSelection ( Point selection ) { } public void setText ( String string ) { } public void setTextLimit ( int limit ) { } public void setVisibleItemCount ( int count ) { } void subclass ( ) { } boolean translateTraversal ( MSG msg ) { } boolean traverseEscape ( ) { } void unsubclass ( ) { } String verifyText ( String string , int start , int end , Event keyEvent ) { } int wcsToMbcsPos ( int wcsPos ) { } int widgetExtStyle ( ) { } int widgetStyle ( ) { } TCHAR windowClass ( ) { } int windowProc ( ) { } int windowProc ( int hwnd , int msg , int wParam , int lParam ) { } LRESULT WM_CTLCOLOR ( int wParam , int lParam ) { } LRESULT WM_GETDLGCODE ( int wParam , int lParam ) { } LRESULT WM_KILLFOCUS ( int wParam , int lParam ) { } LRESULT WM_LBUTTONDOWN ( int wParam , int lParam ) { } LRESULT WM_SETFOCUS ( int wParam , int lParam ) { } LRESULT WM_SIZE ( int wParam , int lParam ) { } LRESULT wmChar ( int hwnd , int wParam , int lParam ) { } LRESULT wmClipboard ( int hwndText , int msg , int wParam , int lParam ) { } LRESULT wmCommandChild ( int wParam , int lParam ) { } LRESULT wmIMEChar ( int hwnd , int wParam , int lParam ) { } }

Fix:
state &= ~ ( ( CANVAS ) | ( TRANSPARENT ) ) ;